com.bigdata.io.LongPacker Maven / Gradle / Ivy
/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
[email protected]
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on Oct 24, 2005
*/
package com.bigdata.io;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
/**
* Packing utility for non-negative long values.
*
* @author Bryan Thompson
* @version $Id$
*/
public class LongPacker
{
public LongPacker() {
super();
}
/**
* Packs a non-negative long value into the minimum #of bytes in which the
* value can be represented and writes those bytes onto the output stream.
* The first byte determines whether or not the long value was packed and,
* if packed, how many bytes were required to represent the packed long
* value. When the high bit of the first byte is a one (1), then the long
* value could not be packed and the long value is found by clearing the
* high bit and interpreting the first byte plus the next seven (7) bytes as
* a long. Otherwise the next three (3) bits are interpreted as an unsigned
* integer giving the #of bytes (nbytes) required to represent the packed
* long value. To recover the long value the high nibble is cleared and the
* first byte together with the next nbytes are interpeted as an unsigned
* long value whose leading zero bytes were not written.
*
*
*
* [0|1|2|3|4|5|6|7]
* 1 - - - nbytes = 8, clear high bit and interpret this plus the next 7 bytes as a long.
* 0 1 1 1 nbytes = 7, clear high nibble and interpret this plus the next 6 bytes as a long.
* 0 1 1 0 nbytes = 6, clear high nibble and interpret this plus the next 5 bytes as a long.
* 0 1 0 1 nbytes = 5, clear high nibble and interpret this plus the next 4 bytes as a long.
* 0 1 0 0 nbytes = 4, clear high nibble and interpret this plus the next 3 bytes as a long.
* 0 0 1 1 nbytes = 3, clear high nibble and interpret this plus the next 3 bytes as a long.
* 0 0 1 0 nbytes = 2, clear high nibble and interpret this plus the next byte as a long.
* 0 0 0 1 nbytes = 1, clear high nibble. value is the low nibble.
*
*
*/
static public int packLong(final DataOutput os, final long v)
throws IOException {
/*
* You can only pack non-negative long values with this method.
*/
if( v < 0 ) {
throw new IllegalArgumentException( "negative value: v="+v );
}
/*
* If the high byte is non-zero then we will write the value as a normal
* long and return nbytes == 8. This case handles large positive long
* values.
*/
if( ( v >> 56 ) != 0 ) {
os.write( (byte)((0xff & (v >> 56))|0x80) ); // note: set the high bit.
os.write( (byte)(0xff & (v >> 48)) );
os.write( (byte)(0xff & (v >> 40)) );
os.write( (byte)(0xff & (v >> 32)) );
os.write( (byte)(0xff & (v >> 24)) );
os.write( (byte)(0xff & (v >> 16)) );
os.write( (byte)(0xff & (v >> 8)) );
os.write( (byte)(0xff & v) );
return 8;
}
// #of nibbles required to represent the long value.
final int nnibbles = getNibbleLength( v );
// Is [nnibbles] even? (If it is even then we need to pad out an extra zero
// nibble in the first byte.)
final boolean evenNibbleCount = ( nnibbles == ( ( nnibbles >> 1 ) << 1 ) );
// #of bytes required to represent the long value (plus the header nibble).
final int nbytes = ( ( nnibbles +1 ) >> 1 ) + (evenNibbleCount?1:0);
int nwritten = 0;
if( evenNibbleCount ) {
/*
* An even nibble count requires that we pad the low nibble of the
* first byte with zeros.
*/
// header byte. low nibble is empty.
byte b = (byte) ( nbytes << 4 );
os.write( b );
nwritten++;
// remaining bytes containing the packed value.
for( int i=(nnibbles-2)<<2; i>=0; i-=8 ) {
b = (byte) (0xff & (v >> i));
os.write( b );
nwritten++;
}
} else {
/*
* An odd nibble count means that we pack the first nibble of the
* long value into the low nibble of the header byte. In this case
* the first nibble will always be the low nibble of the first
* non-zero byte in the long value (the high nibble of that byte
* must be zero since there is an odd nibble count).
*/
byte highByte = (byte) (0xff & (v >> ((nbytes-1)*8) ));
byte b = (byte) ( ( nbytes << 4 ) | highByte );
os.write( b );
nwritten++;
for( int i=(nnibbles-3)<<2; i>=0; i-=8 ) {
b = (byte) (0xff & (v >> i));
os.write( b );
nwritten++;
}
}
return nwritten;
}
/**
* Packs a non-negative long value into the minimum #of bytes in which the
* value can be represented and writes those bytes onto the output stream.
* The first byte determines whether or not the long value was packed and,
* if packed, how many bytes were required to represent the packed long
* value. When the high bit of the first byte is a one (1), then the long
* value could not be packed and the long value is found by clearing the
* high bit and interpreting the first byte plus the next seven (7) bytes as
* a long. Otherwise the next three (3) bits are interpreted as an unsigned
* integer giving the #of bytes (nbytes) required to represent the packed
* long value. To recover the long value the high nibble is cleared and the
* first byte together with the next nbytes are interpeted as an unsigned
* long value whose leading zero bytes were not written.
*
*
*
* [0|1|2|3|4|5|6|7]
* 1 - - - nbytes = 8, clear high bit and interpret this plus the next 7 bytes as a long.
* 0 1 1 1 nbytes = 7, clear high nibble and interpret this plus the next 6 bytes as a long.
* 0 1 1 0 nbytes = 6, clear high nibble and interpret this plus the next 5 bytes as a long.
* 0 1 0 1 nbytes = 5, clear high nibble and interpret this plus the next 4 bytes as a long.
* 0 1 0 0 nbytes = 4, clear high nibble and interpret this plus the next 3 bytes as a long.
* 0 0 1 1 nbytes = 3, clear high nibble and interpret this plus the next 3 bytes as a long.
* 0 0 1 0 nbytes = 2, clear high nibble and interpret this plus the next byte as a long.
* 0 0 0 1 nbytes = 1, clear high nibble. value is the low nibble.
*
*
*/
static public int packLong(final OutputStream os, final long v)
throws IOException {
/*
* You can only pack non-negative long values with this method.
*/
if( v < 0 ) {
throw new IllegalArgumentException( "negative value: v="+v );
}
/*
* If the high byte is non-zero then we will write the value as a normal
* long and return nbytes == 8. This case handles large positive long
* values.
*/
if( ( v >> 56 ) != 0 ) {
os.write( (byte)((0xff & (v >> 56))|0x80) ); // note: set the high bit.
os.write( (byte)(0xff & (v >> 48)) );
os.write( (byte)(0xff & (v >> 40)) );
os.write( (byte)(0xff & (v >> 32)) );
os.write( (byte)(0xff & (v >> 24)) );
os.write( (byte)(0xff & (v >> 16)) );
os.write( (byte)(0xff & (v >> 8)) );
os.write( (byte)(0xff & v) );
return 8;
}
// #of nibbles required to represent the long value.
final int nnibbles = getNibbleLength( v );
// Is [nnibbles] even? (If it is even then we need to pad out an extra zero
// nibble in the first byte.)
final boolean evenNibbleCount = ( nnibbles == ( ( nnibbles >> 1 ) << 1 ) );
// #of bytes required to represent the long value (plus the header nibble).
final int nbytes = ( ( nnibbles +1 ) >> 1 ) + (evenNibbleCount?1:0);
int nwritten = 0;
if( evenNibbleCount ) {
/*
* An even nibble count requires that we pad the low nibble of the
* first byte with zeros.
*/
// header byte. low nibble is empty.
byte b = (byte) ( nbytes << 4 );
os.write( b );
nwritten++;
// remaining bytes containing the packed value.
for( int i=(nnibbles-2)<<2; i>=0; i-=8 ) {
b = (byte) (0xff & (v >> i));
os.write( b );
nwritten++;
}
} else {
/*
* An odd nibble count means that we pack the first nibble of the
* long value into the low nibble of the header byte. In this case
* the first nibble will always be the low nibble of the first
* non-zero byte in the long value (the high nibble of that byte
* must be zero since there is an odd nibble count).
*/
byte highByte = (byte) (0xff & (v >> ((nbytes-1)*8) ));
byte b = (byte) ( ( nbytes << 4 ) | highByte );
os.write( b );
nwritten++;
for( int i=(nnibbles-3)<<2; i>=0; i-=8 ) {
b = (byte) (0xff & (v >> i));
os.write( b );
nwritten++;
}
}
return nwritten;
}
/**
* Narrow interface to support packing against different buffer classes.
*
* @author Bryan
* Thompson
*/
public interface IByteBuffer {
/**
* Relative put method for writing a byte[] on the buffer.
*
* @param b
* The byte[].
* @param off
* The offset of the first byte in b to be written on
* the buffer.
* @param len
* The #of bytes in b to be written on the buffer.
*/
void put(final byte[] b, final int off, final int len);
}
/**
* Packs a non-negative long value into the minimum #of bytes in which the
* value can be represented and writes those bytes onto the buffer.
* The first byte determines whether or not the long value was packed and,
* if packed, how many bytes were required to represent the packed long
* value. When the high bit of the first byte is a one (1), then the long
* value could not be packed and the long value is found by clearing the
* high bit and interpreting the first byte plus the next seven (7) bytes as
* a long. Otherwise the next three (3) bits are interpreted as an unsigned
* integer giving the #of bytes (nbytes) required to represent the packed
* long value. To recover the long value the high nibble is cleared and the
* first byte together with the next nbytes are interpreted as an unsigned
* long value whose leading zero bytes were not written.
*
*
*
* [0|1|2|3|4|5|6|7]
* 1 - - - nbytes = 8, clear high bit and interpret this plus the next 7 bytes as a long.
* 0 1 1 1 nbytes = 7, clear high nibble and interpret this plus the next 6 bytes as a long.
* 0 1 1 0 nbytes = 6, clear high nibble and interpret this plus the next 5 bytes as a long.
* 0 1 0 1 nbytes = 5, clear high nibble and interpret this plus the next 4 bytes as a long.
* 0 1 0 0 nbytes = 4, clear high nibble and interpret this plus the next 3 bytes as a long.
* 0 0 1 1 nbytes = 3, clear high nibble and interpret this plus the next 3 bytes as a long.
* 0 0 1 0 nbytes = 2, clear high nibble and interpret this plus the next byte as a long.
* 0 0 0 1 nbytes = 1, clear high nibble. value is the low nibble.
*
*
*
* @param v The unsigned long value.
*
* @return The #of bytes onto which the unsigned long value was packed.
*/
static final public int packLong(final long v, final byte[] pbuf,
final IByteBuffer buf) {
/*
* You can only pack non-negative long values with this method.
*/
if (v < 0) {
throw new IllegalArgumentException("negative value: v=" + v);
}
/*
* If the high byte is non-zero then we will write the value as a normal
* long and return nbytes == 8. This case handles large positive long
* values.
*/
if( ( v >> 56 ) != 0 ) {
pbuf[0] = ( (byte)((0xff & (v >> 56))|0x80) ); // note: set the high bit.
pbuf[1] = ( (byte)(0xff & (v >> 48)) );
pbuf[2] = ( (byte)(0xff & (v >> 40)) );
pbuf[3] = ( (byte)(0xff & (v >> 32)) );
pbuf[4] = ( (byte)(0xff & (v >> 24)) );
pbuf[5] = ( (byte)(0xff & (v >> 16)) );
pbuf[6] = ( (byte)(0xff & (v >> 8)) );
pbuf[7] = ( (byte)(0xff & v) );
buf.put(pbuf, 0, 8);
return 8;
}
// #of nibbles required to represent the long value.
final int nnibbles = LongPacker.getNibbleLength( v );
/*
* Is [nnibbles] even? (If it is even then we need to pad out an extra
* zero nibble in the first byte.)
*/
final boolean evenNibbleCount = ( nnibbles == ( ( nnibbles >> 1 ) << 1 ) );
// #of bytes required to represent the long value (plus the header nibble).
final int nbytes = ( ( nnibbles +1 ) >> 1 ) + (evenNibbleCount?1:0);
int nwritten = 0;
if( evenNibbleCount ) {
/*
* An even nibble count requires that we pad the low nibble of the
* first byte with zeros.
*/
// header byte. low nibble is empty.
byte b = (byte) ( nbytes << 4 );
pbuf[nwritten++] = b;
// remaining bytes containing the packed value.
for( int i=(nnibbles-2)<<2; i>=0; i-=8 ) {
b = (byte) (0xff & (v >> i));
pbuf[nwritten++] = b;
}
} else {
/*
* An odd nibble count means that we pack the first nibble of the
* long value into the low nibble of the header byte. In this case
* the first nibble will always be the low nibble of the first
* non-zero byte in the long value (the high nibble of that byte
* must be zero since there is an odd nibble count).
*/
byte highByte = (byte) (0xff & (v >> ((nbytes-1)*8) ));
byte b = (byte) ( ( nbytes << 4 ) | highByte );
pbuf[nwritten++] = b;
for( int i=(nnibbles-3)<<2; i>=0; i-=8 ) {
b = (byte) (0xff & (v >> i));
pbuf[nwritten++] = b;
}
}
buf.put(pbuf,0,nwritten);
return nwritten;
}
/**
* Read a byte from an {@link InputStream} ala {@link DataInput#readByte()}
*
* @param is
* The input stream.
* @return The byte.
* @throws IOException
* @throws EOFException
* if the end of the file has been reached.
*/
private static byte readByte(final InputStream is) throws IOException {
final int v = is.read();
if (v == -1)
throw new EOFException();
return (byte) (v & 0xff);
}
/**
* Return the #of non-zero nibbles, counting from the first non-zero nibble
* in the long value. A value of 0L is considered to be one
* nibble for our purposes.
*
* @param v
* The long value.
*
* @return The #of nibbles in [1:16].
*/
static public int getNibbleLength( final long v )
{
for( int i=56, j=16; i>=0; i-=8, j-=2 ) {
if( (0xf0 & (v >> i)) != 0 ) return j;
if( (0x0f & (v >> i)) != 0 ) return j-1;
}
if( v != 0 ) throw new AssertionError( "v="+v );
return 1; // value is zero, which is considered to be one nibble for our purposes.
}
/**
* Return the #of non-zero bytes in the packed long value.
*
* @param v
* The long value.
*
* @return The #bytes in [1:8].
*/
static public int getByteLength(final long v) {
// #of nibbles required to represent the long value.
final int nnibbles = getNibbleLength( v );
// Is [nnibbles] even? (If it is even then we need to pad out an extra zero
// nibble in the first byte.)
final boolean evenNibbleCount = ( nnibbles == ( ( nnibbles >> 1 ) << 1 ) );
// #of bytes required to represent the long value (plus the header nibble).
final int nbytes = ( ( nnibbles +1 ) >> 1 ) + (evenNibbleCount?1:0);
return nbytes;
}
/**
* Unpack a long value from the input stream.
*
* @param is The input stream.
*
* @return The long value.
*
* @throws IOException
*/
static public long unpackLong( final DataInput is ) throws IOException
{
int b = is.readByte();
int nbytes;
long l;
if( ( b & 0x80 ) != 0 ) {
// high bit is set.
nbytes = 8; // use 8 bytes (this one plus the next 7).
l = b & 0x7f; // clear the high bit - the rest of the byte is the start value.
} else {
// high bit is clear.
nbytes = b >> 4; // nbytes is the upper nibble. (right shift one nibble).
l = b & 0x0f; // starting value is lower nibble (clear the upper nibble).
}
for( int i=1; i> 4; // nbytes is the upper nibble. (right shift one nibble).
l = b & 0x0f; // starting value is lower nibble (clear the upper nibble).
}
for( int i=1; i> 4; // nbytes is the upper nibble. (right shift one
// nibble).
l = b & 0x0f; // starting value is lower nibble (clear the upper
// nibble).
}
for (int i = 1; i < nbytes; i++) {
// Read the next byte.
b = buf[off++];
// Shift the existing value one byte left and add into the low
// (unsigned) byte.
l = (l << 8) + (0xff & b);
}
return l;
}
/**
* Convenience method unpacks long and throws an exception if the value
* exceeds {@link Integer#MAX_VALUE}.
*
* @param is
* The input stream.
*
* @return The integer value.
*
* @throws IOException
*/
static public int unpackInt(final DataInput is) throws IOException {
final long v = unpackLong(is);
if (v > Integer.MAX_VALUE)
throw new IOException();
return (int) v;
}
/**
* Convenience method unpacks long and throws an exception if the value
* exceeds {@link Integer#MAX_VALUE}.
*
* @param is
* The input stream.
*
* @return The integer value.
*
* @throws IOException
*/
static public int unpackInt(final InputStream is) throws IOException {
final long v = unpackLong(is);
if (v > Integer.MAX_VALUE)
throw new IOException();
return (int) v;
}
}
© 2015 - 2025 Weber Informatics LLC | Privacy Policy